Thanks!
The real downside of OLED is that it's prone to dead/stuck pixels.
Many OLED panels have dead/stuck pixels right out of the factory, which is why OLED panel yield is so low. This high production wastage contributes to the high price.
Even after a unit is completely assembled without dead/stuck pixels, the TV is still likely to have dead/stuck pixels by the time it reaches the end-user.
The problem with OLED is that it is still not a mature technology.
Aside form dead/stuck pixels, blue subpixel still has a short lifespan problem, which is why LG uses 4 white subpixels under a WRGB filter, claiming that this method solves the blue lifespan issue.
But still, their white subpixels are produced from compressed red, green and blue OLED layers, so the blue OLED problem is still there. How long will the blue layer last? We can't rely on LG to give an honest answer, that's for sure.
BTW, I've seen an LG on display, and it really has a stunning picture. However, I noticed that it has a slight color shift when viewed from an angle. View it from the side and you will notice the whites shift slightly yellowish.